High humidity boosts the chances of mold growth from moisture trapped in the wall or the ceiling. Mold-resistant drywall lowers this risk because it’s less hospitable to mold.
Moisture-resistant drywall is treated with mesh or paper with embedded wax. This coating can prevent joint compound from adhering to your drywall, so you need to take special care when finishing.
What Moisture-Resistant Drywall Is and Where It’s Used
Moisture-resistant drywall is commonly green or purple. It is treated to inhibit mold and mildew growth in high-humidity areas. These drywall panels are made of gypsum like standard drywall, but they also have a mold or moisture-resistant core and coatings of wax-embedded paper or fiberglass.
You’ll see moisture-resistant drywall in high-humidity rooms, such as bathrooms, basements, kitchens, and laundry rooms. It’s also commonly used in humid cities where no room is safe from moisture.
When Moisture-Resistant Drywall Makes Sense for a Job
If you’re working in an area where regular drywall is more likely to get moldy or water-damaged, switching to moisture-resistant drywall makes sense. However, it’s more expensive than regular drywall, so carefully consider where it would most benefit your project.
Damp areas such as bathrooms, kitchens, and mud rooms are at the highest risk for mold and mildew. People shower and take baths in a bathroom, exposing the walls and ceilings to constant humidity. Basements and crawl spaces face damage from water leaks and ground moisture.
You don’t need moisture-resistant drywall in an entire kitchen, but it’s useful behind stoves and sinks.
Be aware that mold- and mildew-resistant drywall is not waterproof, so don’t use it for shower walls or other “wet” areas. Choose cement board or other water-resistant materials in these areas.
How It Differs From Standard Drywall During Finishing
Surface material and texture are the biggest challenges when finishing moisture-resistant drywall. The panels are also denser than standard drywall panels, requiring more fasteners to hold them in place.
If you’re working with paperless drywall that’s coated in fiberglass, you need fiberglass tape or mesh tape. Paper tape may give way when damp, which defeats the purpose of moisture-resistant drywall. It also doesn’t adhere as well to the waxy surface. Mesh tape is water-resistant and self-adhesive, making it easier to work with mold-resistant drywall.
A strong finishing technique is crucial, because you need a reliable seal to prevent moisture buildup. Use Hyde’s taping knives to apply a thin, even layer over your tape. A good taping knife helps you apply joint compound evenly while also embedding the tape into your joint.
Wait for each layer to dry completely, and lightly sand it between coats. Laying on compound too quickly or too thick can cause cracks, bubbles, and sagging.
For an extra layer of moisture-resistance, use hot mud instead of all-purpose mud. It dries through a chemical reaction instead of evaporation, which makes it great for high-humidity areas.
When using hot mud, mix small batches for each layer. Use a small, 6-inch knife for the initial layer and larger tape knives to finish. Hot mud dries fast, so use firm pressure to apply it evenly, and feather out your edges to blend the seams.
Tools That Support Clean, Mold-Resistant Finishes
High-quality tools, including Hyde’s drywall accessories, help you apply drywall mud smoothly for a clean finish. Our taping knives and joint knives have ergonomic handles for a comfortable grip to control your pressure.
Thin, even layers give you a better seal, and you’re less likely to damage the wax or fiberglass drywall surface. Choose a taping knife or joint knife with a flexible carbon steel blade to apply mud smoothly and precisely.
Sanding your mud between layers gives you a smooth, even surface, but the dust can prevent the next layer from adhering correctly. Use a cleaning tool, such as Hyde’s drywall sanding sponge, to clean the surface between layers.
Why Knife Flexibility and Control Matter
Using a rigid knife can complicate your drywall project. Flexible blades make it easier to smooth the compound and feather at the edges. These blades are a must when you’re working on non-linear or curved surfaces. The flexibility allows you to control the pressure as the surface changes.
Using flexible knives also helps you avoid damaging the drywall surface by keeping the knife edge away from the wax paper or fiberglass face.
High-quality tools and finishing techniques save you time as well. Applying drywall mud in thin layers and sanding between them may seem labor-intensive, but it saves you from having to come back and rework mistakes once the mud dries. You get a professional result without having to sand and fill multiple times.
Finishing Techniques That Protect the Treated Paper Face
Your first coat of drywall mud sets the foundation for the rest of your job. Make sure you’re covering every joint and seam with an even layer of mud.
Once it's dry, choose the proper sanding tools for an even surface. Use medium-grit (120-150 grit) for the initial sanding and switch to fine-grit sandpaper (180-220 grit) to smooth out any edges or imperfections between layers.
Sanding your drywall mud with a grit that’s too coarse removes too much material. You can expose the tape and damage the drywall surface, which defeats the purpose of installing mold-resistant drywall.
Use Hyde’s dust-free sanders to minimize dust buildup and make cleanup faster. The sander attaches to your wet-dry vac and removes most drywall dust as you go. Finish with a sanding sponge before applying the next coat of joint compound.
Finishing Moisture-Resistant Drywall for Long-Term Performance
Moisture-resistant drywall protects your building’s occupants from hazardous mold buildup, but you have to install it properly for it to work. Be patient and layer coats of compound instead of applying a single, thick coat. This way, you get a stronger seal that keeps mold out of the drywall for a long time.
Visit Hyde for a wide range of drywall tools and accessories to apply each coat of joint compound evenly the first time. Save yourself from reworking your seams by using the right tools for the job.
Alaina Brandenburger
Alaina Brandenburger has been creating content for clients in many industries since 2009. She holds an MS in Marketing and an MA in Fashion Journalism with a knack for investigating. She loves helping people with strategies on how they can reach more people and grow their businesses.